FIG. 1 is a view illustrating an example of a block diagram of a typical rotator-based BB CDR with a clock generator according to an exemplary embodiment of the present invention.
Referring to FIG. 1, the master channel 110 of a phase rotator-based CDR may include a frequency detector (FD, 111) or a phase frequency detector (PFD, 111), a charge pump 112, a loop filter 113, a phase detector 114, a charge pump 115, a loop filter 113, and a voltage controlled oscillator 117. And, each of sub-channel 1 (120), sub-channel 2 (130), . . . , and sub-channel N−1 (140) may include a phase detector 121, a digital loop filter 122, and a phase rotator 123.
The phase rotator-based CDR architecture shown in FIG. 1 is more suitable for parallel I/O applications than voltage controlled oscillator (VCO) based counterparts considering power and area efficiency. The master channel 110, which has a frequency acquisition loop, spreads a phase-locked clock signal to each sub-channel. The frequency acquisition loop needs a frequency detector (FD, 111) or a phase frequency detector (PFD, 111) due to a limited pull-in range of a phase detector (PD). However, this design does not have operational independency among channels unlike the conventional VCO-based parallel designs. This deficiency arises because a VCO should be phase locked to a data stream in the master channel and the remaining rotator-based sub-channels are subjected to a phase-locked VCO clock signal.